From a49573dd2726eae0ea6397bdf67ade318854d730 Mon Sep 17 00:00:00 2001
From: Steve Kemp <steve@steve.org.uk>
Date: Sun, 6 Nov 2022 12:36:36 +0200
Subject: [PATCH] Allow hexadecimal/binary literals.

This closes #78 by adding native support for hexadecimal and binary
literals.  For example:

* `(print 0xff)`
* `(print 0b00000010)`
---
 eval/eval.go      | 16 ++++++++++++++++
 eval/eval_test.go | 14 ++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/eval/eval.go b/eval/eval.go
index 5c13752..0a9292d 100644
--- a/eval/eval.go
+++ b/eval/eval.go
@@ -188,6 +188,22 @@ func (ev *Eval) atom(token string) primitive.Primitive {
 		return primitive.Error(fmt.Sprintf("invalid character literal: %s", lit))
 	}
 
+	// See if this is a number with a hex/binary prefix
+	based := strings.ToLower(token)
+	if strings.HasPrefix(based, "0x") || strings.HasPrefix(based, "0b") {
+
+		// If so then parse as an integer
+		n, err := strconv.ParseInt(based, 0, 32)
+		if err == nil {
+
+			// Assuming it worked save it in our interned
+			// table and return it.
+			num := primitive.Number(n)
+			ev.symbols[token] = num
+			return num
+		}
+	}
+
 	// Is it a number?
 	f, err := strconv.ParseFloat(token, 64)
 	if err == nil {
diff --git a/eval/eval_test.go b/eval/eval_test.go
index aa7acd0..5f01ee8 100644
--- a/eval/eval_test.go
+++ b/eval/eval_test.go
@@ -101,6 +101,20 @@ func TestEvaluate(t *testing.T) {
 		{"#!/usr/bin/yal\n", "nil"},
 		{"#!/usr/bin/yal\n#t", "#t"},
 
+		// integers: in hex
+		{"0xff", "255"},
+		{"0xFF", "255"},
+		{"0xFf", "255"},
+		{"0xfF", "255"},
+
+		// integers: in binary
+		{"0b00000000", "0"},
+		{"0b00000001", "1"},
+		{"0b00000010", "2"},
+		{"0b00000100", "4"},
+		{"0b00001000", "8"},
+		{"0b10000000", "128"},
+
 		// bools
 		{"#t", "#t"},
 		{"true", "#t"},